It is known that, when sailing in the presence of waves, it is preferable, from the points of view of minimizing drift, of maximizing boat speed, and of increasing on-board comfort, not to keep the rudder in a fixed position, but rather to make rapid course corrections in correspondence with each wave. This is particularly important when the direction of the waves coincides with the wind direction, and the boat is sailing close-hauled or, at the opposite extreme, the boat is sailing on a broad reach.
The effect of waves on sailing a sailboat in the former case (closed-hauled, with the waves coming from the same direction as the wind) is explained in detail in the work by Frank Bethwaite entitled “High Performance Sailing”, International Marine/Ragged Mountain Press, 1st edition (1996), ISBN 0-7136-6704-4, pages 305-319.
The types of corrections to be made on a broad reach are explained in the work entitled “This is Sailing” by Jim Saltonstall, ISBN-0713663596, pages 96 and 97.
That type of sailing requires a great deal of attention from a very experienced helmsperson, which limits its field of application to competitive sailing. It would be advantageous also to make that type of correction in recreational sailing, mainly with the aim of improving comfort on board. Unfortunately that is not generally possible, either because the helmsperson lacks the necessary experience, or because the effort required of the helmsperson is excessive compared with what is at stake.
Even in competitive sailing, it would be advantageous to lighten the task for the helmsperson both in order to make the helmsperson less tired, and in order to enable him or her to leave the helm momentarily without the quality of sailing being degraded.
Prior art automatic pilot systems for automatically steering sailboats do not offer any solution to that problem. Such systems generally comprise a wind sensor, a steering compass, a pilot module, and a rudder actuator module for actuating the rudder of the boat. The pilot module receives, as input, signals coming from the compass and from the wind sensor, and generates, as output, control signals for controlling the rudder actuator module in a manner such as to hold a determined sailing direction either relative to North or relative to the wind direction. Such known automatic pilot systems thus keep the boat heading in a fixed direction and do not make the above-mentioned course corrections in correspondence with the waves. As a result, sailing on automatic pilot in the presence of waves is not good in terms of comfort or in terms of performance, especially on the closed-hauled and broad-reach points of sailing.
Document U.S. Pat. No. 5,632,217 discloses such a conventional automatic pilot system.